The ApplyBounce subroutine - Revs on the BBC Micro

       Name: ApplyBounce                                             [Show more]
       Type: Subroutine
   Category: Driving model
    Summary: Apply a bounce to the player's car when it hits the ground
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * ApplyElevation (Part 4 of 5) calls ApplyBounce


 Calculate the following:

   yGravityDelta = A / 2

   yJumpHeight = A / 4

   heightAboveTrack = heightAboveTrack + 1

   spinYawAngleHi = spinYawAngleHi >> 1 with bit 7 set

 and make the crash/contact sound.


.ApplyBounce

 LSR A                  \ Set yGravityDelta = A / 2
 STA yGravityDelta

 LSR A                  \ Set yJumpHeight = A / 4
 STA yJumpHeight

 INC heightAboveTrack   \ Set heightAboveTrack = heightAboveTrack + 1

 SEC                    \ Rotate spinYawAngleHi right, inserting a 1 into bit 7
 ROR spinYawAngleHi

 LDA #4                 \ Make sound #4 (crash/contact) at the current volume
 JSR MakeSound-3        \ level

 RTS                    \ Return from the subroutine

[X]

Entry point MakeSound-3 in subroutine MakeSound (category: Sound)

Make the sound at the current volume level

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Variable heightAboveTrack in workspace Zero page

The car's height above the track, for when it is being dropped from the crane, or jumping from hitting the verge too fast

[X]

Variable spinYawAngleHi (category: Car geometry)

High byte of the amount of yaw angle spin that is being applied to the player's car

[X]

Variable yGravityDelta in workspace Zero page

The distance in the y-axis that the car would fall if the track wasn't there, for use when calculating the outcome of jumps and being dropped from the crane

[X]

Variable yJumpHeight in workspace Zero page

The height of the car's jump (or crane lift), in terms of track lines, which we use to alter the position of the horizon